1. Field of the invention
This invention relates to a flatness control apparatus for a hot rolling mill which controls strip flatness.
2. Description of the Related Art
In a general flatness control apparatus for a hot rolling mill, manipulated actuator values for the rolling mill are determined based on flatness reference values and measured values of flatness meter equipped on the delivery side of the final stand. The position which measures strip flatness is defined the center of strip width as the center of line of rolling mill.
The flatness control apparatus is almost satisfactory when the center of the strip correspond with the center of line. However, in fact there is always no strip in the center of line. The strip is approached at the drive side, the side of the motor of rolling mill, or at the operator side, the side of monitoring room which supervises the rolled strip situation. In such a case, the position which strip flatness is measured by the flatness meter will be different from the actually measured position. It was difficult to control to flatness reference values and that is low accurate for controlling flatness.